The invention concerns a retaining catch for a socket pipe connection having a substantially circular-arcuate catch body on which is arranged a projection projecting from the catch body. The catch body has a catch cross-section in a cross-sectional plane in a radial direction transversely relative to its circular-arcuate longitudinal extent.
Retaining catches of that kind are already known and are used in socket pipe connections for securing the same in relation to tensile forces. Thus, for example, EP 1 046 854 A2 discloses the use of two retaining catches of the general kind set forth for a socket pipe connection in a pipe end, in the form of a socket, of a first pipe, to a pipe end or insertion end of a second pipe, that is to be inserted into the socket. The pipe end of the first pipe, in the form of the socket, usually has in that case a radially inwardly projecting, peripherally extending limiting collar which in the peripheral direction has one or more openings which approximately correspond to the longitudinal extent of a retaining catch or are somewhat larger so that the retaining catches can be introduced into the socket connection by way of the openings. The end of the second pipe, that is to be introduced into the socket, typically has a peripherally extending contact collar which for example is in the form of a weld bead.
In order now to produce a socket pipe connection, usually the pipe portions (socket and insertion end) are firstly fitted together. Then for example two arcuate retaining catches of mirror-image configuration are introduced by way of an opening on the peripherally extending limiting collar on the socket into the interior of the socket until they bear against the contact collar at the insertion end of the second pipe and are then displaced radially towards the left or the right until a respective projection on the retaining catch bears against an edge of the limiting collar. To hold the retaining catches in that position, a spacer—which can be made from a flexible plastic material—can be arranged between the retaining catches. In the assembled position the retaining catches are disposed between the limiting collar of the socket and the contact collar of the second pipe. It is possible overall to achieve a uniform securing action in relation to tensile forces by virtue of a respective retaining catch on the left-hand side and on the right-hand side.
Socket pipe connections of that kind for pipes or shaped pipe portions are used in particular in pipe systems in the drinking water and waste water fields. In such pipe systems the pipes can be subjected to operating pressure of up to 100 bars or more, whereby high levels of longitudinal tensile forces can also act on the pipes.
The pipes in such pipe systems typically involve nominal widths of between DN 80 and DN 1000. In that case, the pipe ends in the form of the socket are usually provided with a peripherally extending sealing chamber and a peripherally extending thrust securing chamber provided in the end region of the socket. A sealing ring can be arranged in the sealing chamber to seal off the socket pipe connection. In the assembled position, the sealing ring bears both against the inside wall of the sealing chamber and also against the outside wall of the end of the second pipe, that is introduced into the socket, in sealing relationship. The thrust securing chamber has in the direction of the socket end a peripherally extending limiting collar which includes a peripherally extending thrust surface—which extends inclinedly relative to the axial extent of the socket. Openings are provided in the peripheral direction in that limiting collar in order to be able to introduce the retaining catches into the socket. The end of a second pipe, that is introduced into the socket, has a peripherally extending contact collar against which the retaining catches bear in the assembled position.
In such socket pipe connections, the longitudinal tensile securing action is implemented by acting longitudinal tensile forces being passed by way of the contact collar of the second pipe end to the retaining catches and then further by way of the peripherally extending limiting collar or its peripherally extending thrust surface into the thrust securing chamber of the socket. A socket pipe connection of the general kind set forth, depending on the respective nominal width of the pipes, is suitable for operating pressures of over 100 bars or admissible tensile forces of up to 200 kN.
For an optimum tensile securing effect with the lowest possible component stressing, the bending radii of the pipes and the retaining catches are matched to the best possible extent. In the ideal case, the outside pipe radius of the pipe end to be introduced into the socket substantially corresponds to the inside radius of a retaining catch and the outside radius of a retaining catch or its outside surface substantially corresponds to the inside radius of the limiting collar or its thrust surface.
As the pipes or shaped pipe portions to be connected however are subject to manufacturing tolerances, the differing bending radii of the components mean that in the assembled position severe bending forces can act on the retaining catches, which in the extreme case can even lead to breakage of a retaining catch. In particular, pipes or socket pipes of ductile cast iron—which are frequently used in pipe systems in the drinking water and waste water fields-, by virtue of their method of manufacture using a centrifugal casting method with a shaping rotating mold, are subject to corresponding manufacturing fluctuations.